1. Field of the Invention
The subject invention relates to diaphragm valves intended to accommodate a high flow of gas.
2. Description of the Prior Art
A prior art diaphragm valve includes a valve housing having a valve chamber that typically is open to the outside of the valve housing. The valve housing may include threads surrounding the valve chamber. An inlet passage extends through the valve housing from an external location to the valve chamber. An outlet passage extends through the valve housing from the valve chamber to a second external location. Thus, a fluid may flow into the inlet passage through the valve chamber and out of the outlet passage. Pipes or tubes are connected to the inlet and outlet passages to accommodate this flow of fluid.
The prior art diaphragm valve further include a resiliently deflectable diaphragm that extends across the valve chamber in juxtaposed relationship to the inlet passage. The diaphragm may be formed from an elastomer or from a thin resiliently deflectable metal. The diaphragm is made from a material selected to prevent reaction with the fluid carried through the valve.
A valve stem is mounted to the valve housing and is engageable with an external surface region of the diaphragm. The valve stem is selectively movable toward and away from the inlet passage and causes the diaphragm to selectively move into or out of sealing engagement with regions of the valve housing surrounding the inlet passage. Thus, the valve stem can be moved toward the valve housing so that the diaphragm is deflected into sealing engagement with portions of the valve housing surrounding the inlet passage for preventing fluid flow through the valve. The valve stem then can be moved away from the valve housing to permit the diaphragm to deflect away from the inlet passage. Thus, fluid is permitted to flow from the inlet passage into the valve chamber and subsequently from the valve chamber into the outlet passage.
Some diaphragm valves are designed specifically for controlling the flow of liquids, while others are designed specifically to control the flow of gases. Many manufacturing processes require controlled amounts of very pure gases. Even, small amounts of ambient gas or other contaminants can adversely affect the manufacturing process. The components of such gas flow systems are manufactured and assembled in ultra clean environments. Fittings and valves for such systems typically are made entirely from metal and must positively prevent seepage of ambient air into the very pure supply of gas accommodated by the system.
Diaphragm valves are well suited for fluid systems that are intended to accommodate pure gases. However, the metal diaphragm of a diaphragm valve is capable of generating only a relatively small amount of deflection. As a result, prior art diaphragm valves have not been well suited for high flow fluid systems. The flow of fluid through a diaphragm valve theoretically can be increased by merely increasing the cross-sectional dimensions of the inlet passage, the outlet passage and the valve chamber. However, a prior art diaphragm valve must be sufficiently deflectable to seal entirely around such a large inlet passage. The metal diaphragm of a prior art diaphragm valve would have to be positioned very close to such a large inlet passage to effectively seal the entire inlet passage with the limited amount of deflection that is possible with a diaphragm. Thus, even though a fairly large inlet passage can be provided, the actual flow through a prior art diaphragm valve would be restricted by the close proximity of the diaphragm to the inlet passage.
Some prior art diaphragm valves have secured a rigid valving member to the side of the diaphragm facing the valve chamber. The rigid valving member is selectively moved by the diaphragm into and out of sealing engagement with portions of the valve chamber surrounding the inlet passage. Prior art diaphragm valves of this type often are referred to as tied diaphragm valves and are intended to achieve both a high flow and a good quality seal around a fairly large inlet passage. In particular, it has been assumed that the valving member secured to and moved with the diaphragm can achieve better sealing around a large inlet passage than the metal diaphragm could achieve without the benefit of thee valving element. Tied diaphragm valves are used successfully in some fluid systems. However, fluid systems intended for highly pure gas flows often cannot tolerate the presence of a weld area in the gas stream. The weldment creates the potential for contamination and defines a potential weak point that can lead to a costly failure of the valve.
Other tied diaphragm valves merely include a threaded bolt that passes axially through the rigid valving member, through the diaphragm and into the valve stem. However, valves of this type create the potential for contaminating air to flow into the valve chamber through microscopic spaces that may exist between the bolt and the valve element.
In view of the above, it is an object of the subject invention to provide a high flow diaphragm valve that is well suited for high volume fluid flows.
It is another object of the subject invention to provide a diaphragm valve that can permit high volume flows while maintaining high purity.
It is a further object of the subject invention to provide a diaphragm valve with a valving element fixed to portions of the diaphragm in the valve chamber without welding.
A further object of the subject invention is to provide a diaphragm valve with a valving element attached to portions of the diaphragm in the valve chamber without providing a passage through the valve element for tieing the valve element to the diaphragm and the valve stem.